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10 Subject Line Tips to Increase Your Email Open Rates in Sales

By: Salesloft Editorial



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We all know that making a good first impression is important. Even if you are the most interesting, funny, entertaining person out there (which we’re sure you are),  a bad first impression can deter people from wanting to get to know you more.

The same is true for subject lines of B2B sales emails. When you send an email, the first thing your prospect will see is the subject line. What you choose to say determines whether they want to open your email and learn more or send it straight to the archives.

No pressure, right?

Luckily, we can help you start off on the right foot.  We analyzed hundreds of millions of interactions to create recommendations based on real data. From word choice to punctuation, this is the only subject line resource you’ll ever need for understanding what works and what does not in multi-touch, multi-channel sales engagement. 

So without further adieu, here are 10 subject line tips to make the best first impression ever.

Tip #1: Craft subject lines with 1 to 4 words.

Empty subject lines perform better than average but suboptimal and can come off as sneaky. At 6 words in a subject line, bad things start to happen to the reply rate. Keep your subject line short and sweet, and leave the good stuff for the email itself.

Examples of 1-word subject lines:

  • Hey
  • Company name
  • Meeting
Bar chart of reply rate success based on the number of words in the subject line



(Sorry. We didn’t mean to yell.)

Tip #3: Asterisks work better than other types of subject line punctuation.

Here are a few hypotheses we’ve developed from our research:

  • Asterisks are attention-grabbing
  • Exclamation marks are fine
  • Questions demand effort
  • Commas are a sign your subject line is too long

A good rule of thumb is to use punctuation sparingly and authentically.

Here are some examples using punctuation:

  • ***Salesloft Meeting***
  • Hello!
  • *Congrats* from Salesloft
Bar chart of reply success rate based on punctuation marks in subject line

Tip #4: Numbers in subject lines are not good.

When you receive an email, you are more likely to open it if you know it was sent to you personally.

Based on our research, we believe that the general sentiment is that impersonal marketing emails are more likely to use numbers in subject lines. Therefore, they’re more likely to be rejected.

Save the numbers for the email itself, not the subject line.

Bar chart of reply success rate based on the use of numbers in subject lines

Tip #5: In subject lines, it is better to mention your own company than the recipient’s name or company.

This seems to indicate two things, one bad and one good:

  1. You would not put a colleague’s first name in a subject line (it may be a signal of spam), and
  2. The use of the sender’s company ties directly to the content of the email (this is a good thing).
Bar chart of reply success rate using variations of personalization in subject line

Tip #6: Greetings work in subject lines.

We studied the use of “Hello,” “Hi,” and “Hey.” It appears that “Hello” is by far the winner with an average of  200% more replies than “Hi” or “Hey”.

It is the perfect balance of pleasant, honest, and slight informality.

Tip #7: If you were referred, say it in the subject.

Unsurprisingly, referrals remain the single best way to engage prospects. Prospects are much more likely to trust you when there is a shared connection.

Ask for referrals and don’t be shy about using them to get in the door with a prospect. It could deliver over a 500% return on your reply rate!

  • *Referral* from Jeremey at Salesloft
  • Jeremey referred me to you
  • Jeremey from Salesloft says hello!

Tip #8: Flattery remains highly effective.

You know the saying “flattery will get you everywhere”? It’s not wrong.

Both “Congrats” and “Congratulations” yielded big returns in subject lines. Of the two, the shorter, friendlier “Congrats” is your best bet for a reply.

  • Congrats from Salesloft!
  • ***Congratulations***
  • Hello and congrats!
Bar chart of reply rate success based on the use of Congrats vs Congratulations   Congrats wins

Tip #9: Break up language is still working.

Loss aversion is a powerful motivator. Not much has changed since high school.

Breaking up is hard to do, but the good news is that break up language has become more professional and delivers 30% more replies on average.

Use words like:

  • Adieu
  • Bugging
  • Miss/ Missed
  • Wrong
  • Goodbye/ Bye

Tip #10: Avoid “influence & persuasion” language in subject lines.

Gains, urgency, and hyperbole are indicators of spam or disingenuous communication.

Here are some specific words to avoid using:

  • “Gains” words: guaranteed; special; quick; exclusive; new; free; better; best; revenue; value; increase; offer; valuable; save; savings; ROI
  • “Urgency” words: need; limited; now; ready; only; last; final; deadline; only
  • “Hyperbole” words: fantastic; amazing; awesome; ultimate
Bar chart of reply rate failure based on inclusion of influence words in email subject line